james harland james harland@rmit edu au
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James Harland [email protected] COSC1078 Introduction to Information Technology Lecture 4 Images. Introduction to IT. 1 Introduction 2 Images 3 Audio 4 Video WebLearn Test 1 5 Computer Fundamentals Assignment 1

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introduction to it
Intro to ITIntroduction to IT

1 Introduction

2 Images

3Audio

4Video WebLearn Test 1

5 Computer Fundamentals Assignment 1

6 Computer Fundamentals

7Computer Fundamentals

8 Operating Systems WebLearn Test 1

9 Operating Systems Assignment 2

10 Internet

11Internet Security WebLearn Test 3

12Future of IT Assignment 3, Peer and Self Assessment

overview
Intro to ITOverview
  • Questions?
  • Images
  • Assignment 1
  • Lab classes
  • Questions?
introduction
Intro to ITIntroduction

James Harland

  • Email:[email protected]
  • URL:www.cs.rmit.edu.au/~jah
  • Phone:9925 2045
  • Office:14.8.13 (Building 14, level 8, room 13)
  • Consultation:Wed 1.30-2.30, Thu 11.30-12.30

What colour is my office door? Carpet? Chair?

representing colours
Representing Colours

01010100001010101010100110100010101001101001010010100011100010101010100101111001001010…

R

Pixel

G

B

Lecture 4: Images

Intro to IT

representing colours1
Representing Colours
  • There are various different schemes for representing colours
  • RGB
  • CMYK
  • HSB
  • HSL
  • CIE XYZ

01010100001…

Lecture 4: Images

Intro to IT

slide7
RGB
  • Human eye uses red, green, blue sensors
  • Additive --- more colours means lighter colour

+

yellow

+

cyan

+

magenta

+

+

Other colours by varying amounts of R, G, B

Lecture 4: Images

Intro to IT

slide8
RGB
  • Often represented as (#R, #G, #B) where #R, #G, #B in range 0, 1, …, 255 (ie 28 -1)
  • This means 8 bits per channel, or bit depth 24
  • Gives 2563 = 16,777,216 colours overall
  • Note that RGB is a scheme, not a particular set of numbers

Lecture 4: Images

Intro to IT

rgb 8 bits per channel
RGB 8 bits per channel

Lecture 4: Images

Intro to IT

slide10
CMYK
  • Based on 4 colours
  • Subtractive – more colours means less light

Cyan

Magenta

Yellow

blacK

+

yellow

+

cyan

+

magenta

Lecture 4: Images

Intro to IT

cmyk why black why not cmy
CMYK Why Black? Why not CMY?

+

+

  • Used mainly in printing (“4-colour print”)
  • In practice, doesn’t look “black”
  • “There is no colour with more shades than black”
  • Too much ink to make black soaks the paper too much
  • Text is traditionally black (and lots more text than pictures in colour)
  • Black ink is cheaper than coloured

Lecture 4: Images

Intro to IT

representing colours2
Representing Colours
  • There are various different schemes for representing colours
  • RGB
  • CMYK
  • HSB
  • HSL
  • CIE XYZ

01010100001…

Lecture 4: Images

Intro to IT

hsb or hsv
HSB (or HSV)

How do humans describe colour?

“rich dark green”

Hue: basic colour (red, green, blue, yellow, …)

Saturation: amount of colour (intensity, purity)

Brightness: light or dark or in-between …

Can be thought of as a cone or cylinder or hexacone

Lecture 4: Images

Intro to IT

hsb and hsv and hsl
HSB and HSV and HSL
  • Hue is represented on a circle, and hence as a bearing (like on a compass)
  • Saturation and Brightness/Value are percentages
  • HSL is similar, except that 100% luminance is always white (just as 0% brightness is black)

Lecture 4: Images

Intro to IT

cie xyz
CIE XYZ
  • Standard derived from work in 1931 to identify all colours visible to humans
  • Colours divided into brightness and chromacity
  • Humans can see more colours than a typical monitor can display
  • RGB produces more colours than CMYK

Lecture 4: Images

Intro to IT

assignment 1
Intro to ITAssignment 1
  • Use GIMP (or a similar tool) to perform some manipulations on an image
  • Address two issues in relation to this
  • Lab classes 2 and 3 will be based around GIMP
  • Main emphasis is on process, not result!
  • Will be released (on the Learning Hub) by Wednesday 10th March (later today)
lab classes
Lab Classes

Start in week 2 (this week)

Work on practical exercises and sometimes assignment materials

Lab assists present to help and an answer questions

Details will be in the Learning Hub

Lecture 4: Images

Intro to IT

conclusion
Intro to ITConclusion
  • Go to laboratory classes (and tutorials) this week!
  • Lab notes in the Learning Hubub
  • Check details in Course Guide
  • Start reading (notes, problems, report topic)

GET THE BOOK!

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